The present research of the structure and biological activity of immunoglobulins of different classes and subclasses will be continued. Monoclonal proteins formed in patients with plasma cell dyscrasias are being screened and the myeloma proteins used for the biological and structural studies. Two myeloma proteins which could not be classified into one of the well known classes and subclasses of human immunoglobulins were detected in the last year and it will be attempted to characterize these proteins and to search for their normal counterparts. Studies of the cytophilic property of immunoglobulins to neutrophils, monocytes and lymphocytes will be continued. Specific emphasis will be placed on the lymphocytes (B, T or "killer" lymphocyte) which have receptors for IgG1 and IgG3. In vivo experiments of the role of IgD bearing lymphocytes will be initiated.